The present invention relates to a cold-water-swelling granular starch which is characterized by a high cold-water solubility and to a process for its preparation. The present invention also relates to the use of the novel starch material as a gelling or thickening agent in food systems, particularly those of the type which set or gel on standing.
Most common of the food systems which have a set or a gel texture are dessert formulations such as pie fillings, puddings and jellies. Many food systems of this description contain a starch gelling agent which must be cooked in the formulation to effect gelation. An example of a such food product which requires cooking to effect gelation is the conventional starch-based pudding, which generally consists of ungelatinized starch, flavorings, sweetening agents, coloring material and other food acceptable adjuvants such as emulsifiers. Such puddings are prepared for consumption by adding milk, cooking until the starch is gelatinized, pouring the cooked mixture into a bowl or individual serving dishes, and cooling and/or refrigerating. The starch used in such cooked food formulations can be common food grade ungelatinized corn starch or starches derived from potato, tapioca, and wheat which will when acid-converted to certain water fluidity levels, retrograde to a gel when cooked. Other common gelling agents used in the past for cooked food compositions include agar, gelatin, pectin, carrageenin, algin, and combinations of locust bean gum and xanthan gum.
To avoid the inconvenience associated with food systems requiring cooking and subsequent chilling to achieve the desired gel structure, there has been developed and described in the art a number of gelling or setting agents and combinations thereof which will effect gelling of a food composition without cooking. Most food systems utilizing such no-cook gelling agents are milk-based and consist of chemically modified pregelatinized starch, one or more setting agents, which are usually phosphate salts, and flavoring, sweetening, and coloring agents. The set or gel properties of these food systems are obtained from the interaction from the phosphate salts with the casein and calcium ions provided by the milk, and not from the starch ingredient in the formulation. In such systems the pregelatinized starch functions as a viscosity builder or thickening agent, but does not play a primary role in the development of the gel structure of the prepared food system.
One major drawback of many of these uncooked or instant food formulations is that they do not have the firm gel structure such as that obtainable in the cooked formulations; that is, they do not cut as cleanly with a spoon, and their texture rather than being smooth, is generally described as "grainy" in both appearance and mouth-feel. Moreover, setting salt gelling combinations are not operative at low pH or in non-milk-based food systems.
The development of a no-cook or instant gelling food composition which has properties such as texture, appearance, gel structure and flavor which closely resemble those of comparable food formulations which are cooked has been the goal of a number of research and development efforts in the starch and food industry. Most success in the development of no-cook, starch-based gelling compositions has been found with chemically modified, pregelatinized starches (particularly those derived from potato and tapioca) and combinations of pregelatinized starch with other starch-based ingredients.
Germino, U.S. Pat. No. 3,583,874 discloses a starch composition suitable as a gelling agent in instant puddings which comprises a blend of pregelatinized, defatted starch and a granular preswollen starch having a water fluidity in a certain range.
Kuchinke, U.S. Pat. No. 3,332,785 describes a cold setting pregelatinized starch material which is prepared by heating starch in an aqueous slurry with an organic carboxylic acid to 90.degree. to 95.degree. C. until the starch is completely gelatinized and thereafter spray drying the mixture.
Chiu, U.S. Pat. No. 4,228,199 describes a chemically modified, pregelatinized, cold-water dispersible gelling potato starch which is useful in preparing instant gelling food compositions. The modified potato starch is prepared by reacting a potato starch with a cross-linking agent to within defined Brabender Viscosity limits sufficient to provide the modified starch with gelling properties and thereafter drum drying the cross-linked starch to obtain the modified gelling potato starch product. Chiu, U.S. Pat. Nos. 4,229,489 and 4,207,355 each describe cold-water dispersible, gelling, chemically modified tapioca starch. The preparation of each of the disclosed gelling tapioca starches involves converting a tapioca starch to a specified water fluidity and reacting the starch with a cross-linking agent to within defined Brabender Viscosity limits. The modified tapioca starch described in the '489 patent is prepared by first reacting tapioca starch with cross-linking agent, acid converting the cross-linked starch and then drum drying the cross-linked and converted starch to provide a chemically modified, pregelatinized starch material with gelling properties.
In addition to the chemically modified, pregelatinized starches which have been developed for instant gelling food systems, there is also disclosed in Mitchell, U.S. Pat. No. 4,260,642 the preparation of instant pudding starches through modification of a starch by forming an aqueous slurry containing an ungelatinized starch and an effective amount of sodium or calcium stearoyl-2-lactylate and heating the slurry to a temperature and for a period of time sufficient to gelatinize the starch. That patent discloses that the resultant modified starch possesses a smoother, creamier mouth-feel and higher sheen than does a starch pregelatinized without sodium or calcium stearoyl-2-lactylate. In one preferred embodiment of that invention, an aqueous slurry of ungelatinized starch is heated in the presence of calcium or sodium stearoyl-2-lactylate for a period of time sufficient to gelatinize the starch and to obtain whole granules uniformly swelled while minimizing bursting and undercooking of the starch granules and drying the slurry.
In view of recent trends and preference for the use of "natural" (not chemically modified) ingredients in food preparations, a starch preparation which is unmodified by reaction with chemical modifiers or one which has been subjected to only a minimal amount of chemical modification or derivatization would offer several obvious advantages for use in gelled food systems. Not only would the cost of chemical modifying agents be eliminated or minimized but also there would be the inherent advantage perceived by the consumer of minimizing or eliminating the chemically modified starch ingredients in the many gelled or starch thickened food compositions which are included in the consumer's diet.
Accordingly, it is an object to the present invention to provide a granular starch material, having little or no chemical substitution or modification which is useful as a thickening or gelling agent for instant food formulations.
It is a further object of this invention to provide an instant gelling food composition which has the texture, appearance, gel structure and flavor which resemble those of comparable starch-based cooked food formulations.
Another object is to provide a process for converting ungelatinized granular corn starch having little or no cold-water solubility to a granular starch product which has a cold-water solubility of at least 50% and is useful as a thickening agent in no-cook food formulations.
Still another object is to provide a process for the preparation of starch gelling agents suitable for use in instant gelled food formulations which does not involve the modification of starch by reaction with chemical modifiers.
A further object of this invention is to provide a unique cold-gelling granular starch material, not modified chemically, but having a cold-water solubility of at least 50%.
It is still another object of the present invention to provide instant gelled food compositions having the texture, appearance and flavor of cooked starch-containing gelled food formulations by utilizing as the gelling agent a granular starch material which has not been chemically modified by reaction with chemical reactants.
The above and related objects are achieved in the present invention by a novel cold-water-swelling granular starch material derived from ungelatinized corn starch. The improved cold-water-swelling granular starch material consists essentially of substantially intact, partially swollen granules which appear nonbirefringent when viewed under a polarizing microscope. It is further characterized by a cold-water solubility of at least 50% and, where the ungelatinized corn starch starting material for the present starch is not modified chemically or minimally modified, by an ability to set, without cooking or chilling, to a resilient, cleanly sliceable gel when blended with an aqueous sugar syrup. The present cold-water-swelling/cold-water-soluble starch material is prepared by forming a slurry of granular ungelatinized corn starch in a liquid medium comprised of water and either ethanol, denatured ethanol, propanol or isopropanol; and heating said slurry to a temperature of about 300.degree. to about 360.degree. F. at or above autogenic pressure for about 1 to about 30 minutes. The cold-water-swelling granular starch material is then separated from the processing medium by filtration, centrifugation, decantation and like means.
Cold-water-swelling granular starches, that is, granular starches which, when added to cold water, will rapidly swell and disperse into water to form a smooth viscous paste, are not unknown in the art. Generally, cold-water-swelling granular starch products have been prepared either by chemical modification, especially hydroxyalkylation such as that described in Kisler, U.S. Pat. No. 2,516,634, or by so-called physical modification wherein granular starch is not modified chemically by reaction with starch-reactive chemical modifiers, but instead is subjected to conditions which cause the individual granules to swell to the extent that they lose birefringence but not to the extent that the granules burst. Typical of the conditions for such "physical modification" of granular starch is heating starch above the granular swelling temperature in the presence of water and gelatinization inhibitors or in the presence of amounts of water (or other liquids capable of gelatinizing starch) insufficient to effect gelatinization (granular disintegration).
The process for preparing the present cold-water-swelling granular starch material can be characterized as a physical modification procedure. There are a number of prior art patents which disclose cold-water-swelling granular starch products prepared by processes embodying apparent physical modifications of granular starch, or apparent combinations of physical and chemical modifications of granular starch.
Drittler, U.S. Pat. No. 847,658 describes a granular cold-water-swelling starch material which is prepared by mixing dry powdered commercial starch with a suitable quantity of a liquid hydrocarbon or hydrocarbons and then adding a suitable quantity of caustic alkali. The granular starch product thereby produced swells in cold water to form a viscous paste-like mass. Edson U.S. Pat. No. 1,956,064 describes the preparation of a dextrinized cold-water-swelling granular starch by heating granular starch to 400.degree. F. in an oven. The product is dispersed in cold water by stirring to provide starch pastes which are useful as adhesives and apparently do not set to a gel on standing.
Kesler, U.S. Pat. Nos. 2,121,502 and 2,124,372 each describe and claim methods for preparing nonbirefringent granular starch products comprising heating raw starch in water in the presence of a disintegration inhibitor to a temperature sufficient to swell the granules to an extent that they lose birefringence but before the bulk of said granules have disintegrated. The '372 patent discloses the use of surfactant type compounds as disintegration inhibitors while the '502 patent discloses the use of volatile inhibitors such as hydrogenated phenols. The swollen granular products in each case are disclosed as useful in the manufacture of paper and are said to remain suspended (in water) at concentrations at which ordinary starch would settle out. There is no disclosure of the high water-solubility characteristic of the starches of the present invention.
Carey, U.S. Pat. No. 3,067,064 discloses the preparation of a thin-boiling, free-flowing starch material characterized by swollen cells and unbroken cell walls which product is prepared by tempering granular starch material at a temperature below its gelatinization temperature to a moisture content of 27 to 42% and thereafter heating the starch material in the semi-dry state in the presence of live steam until the cells in the starch material are swollen and unruptured, that is until the granules lose birefringence, as measured by the so-called maltese-cross test. The patent discloses that on boiling a 10% suspension of the described starch material, it did not thicken appreciably nor did it form a gel on cooling.
Bernetti, U.S. Pat. No. 3,399,081 describes the preparation of nonbirefringent granular starches which exhibit cold paste viscosities on initial dispersion in cold water by treating granular starch with mixtures of ammonia and methanol at low temperature. By use of a high concentration of ammonia and an excess of methanol, it is disclosed that a product is produced that has a swelling power at 25.degree. C. of 17, solubles value of 36% and a fat content of 0.4%. The starch products are described as useful laundry starches.
Thurston, U.S. Pat. No. 3,617,383 describes and claims a continuous process for preparing a cold-water-swelling granular starch having 40 to 100% loss of birefringence by (1) preparing a slurry of a granular ungelatinized starch material in a mixture of a solvent for starch, including water, and an organic liquid which is miscible with the solvent for the starch material and which is not itself a solvent for the starch material, said miscible organic liquid including lower alcohols; and (2) passing that slurry through a heated confined zone. A preferred processing medium for the disclosed process is a mixture of water and methanol. The '383 patent does not disclose granular cold-water-swelling starch products having the high water solubility and gelling properties characteristic of the chemically unmodified cold-water-swelling starches of the present invention, nor does it exemplify process conditions capable of producing the present starch material.
Germino, U.S. Pat. Nos. 3,717,475 and 3,586,536 describe a continuous fat extraction process wherein granular starches having a normal amount of bound fat are first mixed with a solvent for said bound fat, the resultant mixture containing not more than 15% of water based on the weight of the total mixture and thereafter heating the mixture in a confined zone at a temperature of about 225.degree. to 300.degree. F. for a time sufficient to reduce the bound fat content of the starch to not more than 0.15%. One goal of the disclosed process is to provide defatted starches having no incipient gelatinization. Incipient gelatinization is said to exist if more than 2% of the granules showed anything from a swelling of the hilums of the granules to a complete loss of birefringence. Several examples in that patent describe the heating of converted thin-boiling granular starch in mixtures of lower alcohols and water to provide granular starch products which are outside the scope of the claimed invention because they were said to have incipient gelatinization. Applicants have found that the conditions of those examples, even when applied to unconverted granular starch, do not provide starch products having the water-solubility characteristics of the cold-water-swelling granular starch products of the present invention; indeed, ethanol and isopropanol are taught as inoperative in the process disclosed therein.
Bruner, U.S. Pat. No. 4,104,212 describes the preparation of granular cold-water-swelling starches which are useful as thickeners for latex compositions. The cold-water-swelling starch is prepared by heating granular starch in an aqueous slurry to about 167.degree. F. for 30 seconds followed by spray drying. A 10% aqueous slurry of the described starch products is said to exhibit a Brookfield Viscosity of 150 to 650 centipoise. A 10% aqueous slurry of a cold-water-swelling granular starch of the present invention exhibited a Brookfield Viscosity of 44,500 centipoise.
Mitchell, U.S. Pat. No. 4,260,642 discussed hereinabove describes a process for preparing a pregelatinized modified starch suitable for use in instant puddings by forming an aqueous slurry containing an ungelatinized starch and an effective amount of sodium stearoyl-2-lactylate and heating the slurry to a temperature for a period of time sufficient to gelatinize the starch and to obtain whole starch granules uniformly swelled while minimizing bursting and undercooking of starch granules. The modified starch material according to the '642 patent does not exhibit the cold-water solubility of the present granular starch.
The cold-water-swelling granular starch material of applicants' invention is distinguished from the cold-water-swelling granular starch materials disclosed in the prior art by its unusual high water-solubility (compared to other granular starches which have not been modified chemically, such as by hydroxypropylation, with the purpose of imparting that characteristic).
In addition, the starch materials prepared in accordance with the present process from ungelatinized corn starch having little or no prior chemical modification have the unique ability (as a granular starch material) to set without cooking or chilling to a resilient, cleanly sliceable gel when blended with an aqueous sugar syrup. Heretofore, gelling characteristics resembling those exhibited by such of the present granular starch materials have been seen only in chemically modified, pregelatinized starches. "Pregelatinized" as used herein (and commonly in the art) with reference to prior art starch materials refers to starch materials in which little if any of the starch is in granular form; the granules therein have been substantially fragmented, burst, or disintegrated by processing.
The cold-water-swelling, cold-gelling starch material of the present invention is useful in any food formulation where a starch which will gel without further cooking is desired, and is particularly suited for use in pie and cream fillings, puddings, spreads, jellies, and instant mixes of the type which are reconstituted with water or milk and allowed to set at room temperature or lower. The present starch materials also can be used alone or in combinations with other starch materials as a thickening agent for other food compositions commonly containing a starch thickening agent including, for example, sauces and gravies. An instant food system containing the present starch will have a texture, appearance, and flavor which closely resembles that of a starch-thickened or gelled food formulation which has been cooked.